This invention relates to a unique placement for an unloader valve, that is particularly beneficial in a scroll compressor.
Scroll compressors are becoming widely utilized in compression applications. However, scroll compressors present several design challenges. One particular design challenge is achieving reduced capacity levels when full capacity operation of the compressor is not desired. In many situations, it may not be desirable to have full capacity of the compressor. In particular, in many refrigeration or refrigerant compression applications, there are times when it would be more desirable to have the ability to achieve reduced capacity.
Thus, scroll compressors have been provided with unloader bypass valves which divert a portion of the compressed refrigerant back to a suction port for the compressor. In this way, the mass of refrigerant being compressed is reduced.
On the other hand, in many refrigeration or refrigerant compression applications, there are other times when it would be more desirable to have the ability to also achieve increased capacity. One way of achieving increased capacity is the inclusion of an economizer circuit into the refrigerant system. An economizer circuit essentially provides heat transfer between a main refrigerant flow downstream of the condenser, and a second refrigerant flow which is also tapped downstream of the condenser and passed through an expansion valve. The main flow is cooled in a heat exchanger by the second flow. In this way, the main flow from the condenser is cooled before passing through its own expansion valve and entering the evaporator. Since the main flow enters the expansion valve at a cooler temperature, it has greater capacity to absorb heat which results in increased system cooling capacity, which was the original objective. The refrigerant in the second flow enters the compression chambers at a point slightly downstream of suction at an intermediate compression point. Typically, the economizer fluid is injected at a point after the compression chambers have been closed.
It would be desirable to combine the features of selectively reduced capacity and increased capacity within the same compressor and system. Conventional practices would dictate independent sets of ports, passages, valves, and controls for the dual capability. Such proliferation of features also dictates increased complexity and cost to manufacture.